The current digital display systems having micromirror arrays or other similar spatial light modulators such as ferroelectric LCDs, uses pulse-width-modulation (PWM) to achieve various levels of light intensity on each of the pixels of the spatial light modulator. Full-color images may be created by using the PWM method on separate SLMs for each primary color, or by a single SLM using a field-sequential color technique.
For addressing and controlling the states of the micromirrors, each micromirror of the spatial light modulator is associated with a memory cell circuit that stores a bit of data that determines the ON or OFF state of the micromirror. In order to achieve various levels of perceived light intensity by human eyes using PWM, each pixel of a grayscale image is represented by a plurality of data bits. Each data bit is assigned a significance. Each time the micromirror is addressed, the value of the data bit determines whether the addressed micromirror is on or off. The bit significance determines the duration of the micromirror's on or off period. The bits of the same significance from all pixels of the image are called a bitplane. If the elapsed time the micromirrors are left in the state corresponding to each bitplane is proportional to the relative bitplane significance, the micromirrors produce the desired grayscale image.
In practice, the PWM coding, the color filter cycling and the operations of other components of the display systems, such as image data processing and loading the processes data into the spatial light modulator to produce the desired images or videos must be coordinated with each other.
Therefore, a control unit is desired to control the operation of the display system.